So for our robot proposal our team decided to physically build as we built on Lego Digital Designer. This made for better "reality testing", so that we knew if our designs would actually work if programmed and put to the test on the field. Our final design had a long ferris-wheel arm for retrieving the water/ice & helium samples; 8 wheels strategically placed to provide maximum awesomeness; and an NXT where it could balance the weight of the arm.
The idea behind our retrieval arm is that if you use a simple lifting arm, you run the risk of dropping the samples when you lower your arm for more samples. So we decided to use a ferris-wheel idea that rotated each sample backwards, slid the samples onto a safety hook, and kept moving all at the same time.
Our wheels are built along the idea of a swerve drive. Now, if you don't know what that is, a swerve drive has one set of turning wheels in the front, and a set of powered wheels in the back. However, our idea is a bit altered.
Each wheel of the 4 wheels in the turning set is connected to a large gear above it. The gears are all interconnected, so that as one motor turns a gear, the wheels all turn in sync. The gear ration is set for torque, which means that the wheels can't be forced straight even if the powered wheels are pushing hard. It also allows for sharper and more sudden turns if needed.
The powered wheels are a whole different story. All of the 6 powered wheels are set at specific intervals, first of all so they turn the same way, but also so that certain sets have more torque, (meaning they push hard, but slowly), and others are geared for speed, (meaning they push fast, but they are weak). The shape of the gear train is also strange, as it isn't straight, but instead it is like an upside down "V" shape. This special shape is because of the crates and ridges that are set up around the Moonbots map. As we built our robot, we discovered that having a straight gear train wouldn't work because it got caught on the lip of the craters' ridges. However, the upside down "V" shape is perfect for the job, as it neatly avoids even coming close to the ridges.